Enhanced oil recovery process

ABSTRACT

A method for recovering oil by injecting oxygen into an underground oil formation where in-situ combustion occurs. The oxygen may be co-injected with additional components to assist in the recovery of the oil, or it may be injected after the injection of the additional components sequentially. The recovered oil may be used in an integrated process above ground for the combustion and generation of power.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Patent Application Ser. No. 61/521,436 filed Aug. 9, 2011.

BACKGROUND OF THE INVENTION

The invention relates to oxygen induced underground in-situ combustion (ISC) for enhanced oil recovery (EOR).

In-situ combustion has been used in oil fields but has typically used air as an oxidant in the past. This can result in lower process efficiencies and reliability issues in the overall process.

The invention uses the injection of oxygen with or without a controlled amount of another co-injected fluid such as carbon dioxide, water and/or hydrocarbons. The invention further utilizes the in-situ combustion to assist in carbon dioxide and steam coproduction.

SUMMARY OF THE INVENTION

The invention provides for enhanced oil recovery utilizing the injection of pure oxygen or a mixture of oxygen with selected fluids. This invention further provides for underground in-situ combustion of virgin oil or residual/heavy oil fractions with oxygen, with or without other co-injected or sequentially injected fluids. The co-injected or sequentially injected fluids are selected from the group consisting of carbon dioxide, water, air and hydrocarbons.

In a first embodiment, there is disclosed a method for in-situ combustion in an enhanced oil recovery process comprising injecting oxygen into an underground oil formation.

In another embodiment, there is disclosed a method for in-situ combustion in an enhanced oil recovery process comprising injecting a mixture of oxygen and a component selected from the group consisting of carbon dioxide, water, air and hydrocarbons into an underground oil formation.

In a different embodiment, there is disclosed a method for in-situ combustion in an enhanced oil recovery process comprising sequentially injecting oxygen and then a component selected from the group consisting of carbon dioxide, water, air and hydrocarbons into an underground oil formation.

In a different embodiment, there is disclosed a method for enhanced oil recovery process comprising sequentially injecting one or more components from the group consisting of carbon dioxide, water, air and hydrocarbons into an underground oil formation, followed by the injection of pure oxygen or oxygen mixed with one or more components from the group consisting of carbon dioxide, water, air and hydrocarbons leading to controlled in-situ combustion of virgin oil, residual/heavy oil and/or coinjected fuel components inside the same oil formation.

The oxygen that is injected into the underground oil formation is produced in an oxygen production plant such as an air separation facility. The oxygen is injected through an injection well into the underground oil formation and the oil is recovered from the underground oil formation through production wells.

The oil that is recovered through the production wells contains impurities such as waste liquids and solids and gas. This oil mixture is fed to a gas, liquids, solids separator wherein the waste liquids and solids are removed and the oil recovered for storage, use or further processing. The coproduced gas is fed to a fuel feed line where either alone or optionally with additional fuel is fed to an integrated process for combustion, power generation, fluid separation, compression and recirculation. Some gas or liquid may be removed from the separator and is fed to the oxygen injection line into the injection wells to provide some recirculation.

In the case of oxygen injection alone, there may optionally be carbon dioxide and/or water injected into the injection well. This injection can be done as a mixture of all three or maybe the sequential addition of oxygen, carbon dioxide and/or water into the injection well. The carbon dioxide and the water may be recovered from the integrated process and can be fed directly into the oxygen injection line into the injection well. Further carbon dioxide may also be recovered from the integrated process and recovered as carbon capture, utilization and/or sequestration (CCUS) ready carbon dioxide or as a source for carbon dioxide based enhanced oil recovery transported through a carbon dioxide pipeline for EOR of remote oil formations or injected in a nearby oil reservoir suitable for a CO₂ based EOR

Some oxygen from the oxygen production plant may be diverted and fed into the integrated process as a fuel for combustion and power generation. This power can then be fed to the oxygen production plant.

The invention allows for the integration with other process options to perform other specific functions. For example, the utilization of associated gas coproduced with oil and other available hydrocarbon fuels, including low heating value waste fuel streams, can be used to separate carbon dioxide from hydrocarbons and/or to convert the fuels into carbon dioxide by performing advanced, thermal oxy-fuel combustion or full catalytic oxidation of hydrocarbons. This will also result in the coproduction of substantial amounts of thermal energy which in turn can be converted to electrical energy to provide power for the entire integrated process on the surface. This energy can be used in the oxygen production plant, for the compression of oxygen, carbon dioxide and other fluids being injected underground, for carbon dioxide recirculation with or without its liquefaction as well as for the net electrical power and carbon capture and its storage or its utilization for EOR ready carbon dioxide exports.

Further, depending upon the selected integrated process option, some of the process variants include high pressure oxy-fuel combustion integrated with power generation. Other surface integrated process options include utilization of the potential energy of pressurized associated gas for power generation by utilizing gas expanders.

The underground in situ combustion of virgin oil and/or residual oil fractions with oxygen facilitates in-situ carbon dioxide and steam coproduction which further enhances oil recovery by combining thermal and gas-oil miscible EOR mechanisms. Depending on the oil and reservoir properties, a combination of injected oxygen with water and/or recirculated and/or coproduced carbon dioxide could further enhance oil recovery above that achieved only by in-situ underground production of carbon dioxide and steam. A variety of arrangements are anticipated to be employed by the invention. For example, different injection schemes and well arrangements such as horizontal versus vertical and single versus multiple wells can be used by the invention. The different wells can be positioned at the same underground depth or below the injection point of oxygen.

The invention is also directed to means of sequestering excess amounts of coproduced carbon dioxide by injecting it into already explored oil reservoirs. The excess carbon dioxide can also be used advantageously as the initial carbon dioxide supply for subsequent oxygen and carbon dioxide injection based EOR processes in the same region by virtue of the pressure drive transportation of carbon dioxide by surface carbon dioxide pipelines. The excess carbon dioxide can be also further purified in the integrated surface facility and exported as a pipeline quality CO₂ for its further utilization, including CO₂ based EOR in remote locations. In particular situations, the integrated surface process is directed towards the liquefaction of captured excess carbon dioxide for its further utilization and distribution as a merchant product for a variety of applications such as food and beverage use.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE is a schematic representation of an integrated process whereby oxygen is injected with or without additional compounds into an underground oil-bearing formation.

DETAILED DESCRIPTION OF THE INVENTION

Turning to the FIGURE, there is described a schematic diagram of a process of injecting oxygen into an underground oil-bearing formation B Oxygen which may be derived from any source such as an air separation plant A is injected into the underground oil-bearing formation B through one or more than one injection well 1A.

The oxygen injected into the injection well or wells will combust in-situ with virgin oil or residual oil or heavy oil fractions which allow for recovery of oil from the production well or wells 3. These production wells can be vertical and/or horizontal in orientation. The oil that is recovered is fed to a separator C which will separate oil which is recovered through line 3A from the waste liquids and solids which are removed through lines 3B and 3C respectively. The coproduced gas is recovered and fed through line 4 to an optional fuel line 5 where it can be fed into the integrated process D.

Oxygen from the oxygen production process can also be fed through line 2 into the integrated process. The integrated process is a process utilizing a series of unit operations to separate fluids, compress and recirculate them as well as combust them and generate power.

As part of the injection of oxygen into the underground oil-bearing formation, water and carbon dioxide may optionally be injected as well and are inputted into the oxygen injection through line 1 through lines 6 and 7 respectively. The coproduced water could be exported through line 6A. Selected gas and/or liquid components may be recovered from separator C and fed through line 11 into oxygen injection line 1 or into a separate injection well 1A.

Power produced from the integrated process may be recovered as electrical power and/or heat through line 9 and may be used for other unit operations within the integrated process or be used in powering the air separation plant A for producing oxygen as supplied through line 10. Carbon dioxide may be recovered from the integrated process as well for carbon capture and its utilization or storage through line 8.

While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of the invention will be obvious to those skilled in the art. The appended claims in this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the invention. 

Having thus described the invention, what I claim is:
 1. A method for in-situ combustion in an enhanced oil recovery process comprising injecting oxygen into an underground oil formation.
 2. The method as claimed in claim 1 wherein said oxygen is injected through injection wells.
 3. The method as claimed in claim 1 wherein oil is recovered from said underground oil formation through production wells.
 4. The method as claimed in claim 3 wherein said oil containing mixture is fed to a separator wherein oil is separated from coproduced gas and any wastes present in the recovered oil.
 5. The method as claimed in claim 4 wherein said wastes comprise waste liquids and solids.
 6. The method as claimed in claim 4 wherein said coproduced gas is fed to an integrated process for fluid separation, combustion, power generation, and fluid compression.
 7. The method as claimed in claim 6 wherein oxygen is injected into said integrated process.
 8. The method as claimed in claim 7 wherein said oxygen is produced in an oxygen production plant.
 9. The method as claimed in claim 8 wherein said integrated process produces electric power for said oxygen production plant.
 10. The method as claimed in claim 9 wherein said integrated process produces carbon dioxide and water.
 11. The method as claimed in claim 10 wherein said carbon dioxide is carbon capture, utilization and/or sequestration ready.
 12. A method for in-situ combustion in an enhanced oil recovery process comprising injecting a mixture of oxygen and a component selected from the group consisting of carbon dioxide, water, air and hydrocarbons into an underground oil formation.
 13. The method as claimed in claim 12 wherein said oxygen is injected through injection wells.
 14. The method as claimed in claim 12 wherein oil is recovered from said underground oil formation through production wells.
 15. The method as claimed in claim 14 wherein said oil containing mixture is fed to a separator wherein oil is separated from coproduced gas and any wastes present in the recovered oil.
 16. The method as claimed in claim 15 wherein said wastes comprise waste liquids and solids.
 17. The method as claimed in claim 15 wherein said coproduced gas is fed to an integrated process for fluid separation, combustion, power generation and fluid compression.
 18. The method as claimed in claim 17 wherein oxygen is injected into said integrated process.
 19. The method as claimed in claim 18 wherein said oxygen is produced in an oxygen production plant.
 20. The method as claimed in claim 19 wherein said integrated process produces electric power for said oxygen production plant.
 21. The method as claimed in claim 20 wherein said integrated process produces carbon dioxide and water.
 22. The method as claimed in claim 21 wherein said carbon dioxide is carbon capture, utilization and/or sequestration ready.
 23. A method for in-situ combustion in an enhanced oil recovery process comprising sequentially injecting a component selected from the group consisting of carbon dioxide, water, air and hydrocarbons and then oxygen into an underground oil formation.
 24. The method as claimed in claim 23 wherein said oxygen is injected through injection wells.
 25. The method as claimed in claim 23 wherein oil is recovered from said underground oil formation through production wells.
 26. The method as claimed in claim 25 wherein said oil containing mixture is fed to a separator wherein oil is separated from coproduced gas and any wastes present in the recovered oil.
 27. The method as claimed in claim 26 wherein said wastes comprise waste liquids and solids.
 28. The method as claimed in claim 26 wherein said coproduced gas is fed to an integrated process for fluid separation, combustion, power generation and fluid compression.
 29. The method as claimed in claim 28 wherein oxygen is injected into said integrated process.
 30. The method as claimed in claim 29 wherein said oxygen is produced in an oxygen production plant.
 31. The method as claimed in claim 30 wherein said integrated process produces electric power for said oxygen production plant.
 32. The method as claimed in claim 31 wherein said integrated process produces carbon dioxide and water.
 33. The method as claimed in claim 32 wherein said carbon dioxide is carbon capture, utilization and/or sequestration ready. 